Voltage selective amplifier



June 10, 1952 DEC/20E l' o. l.. MaCsoRLEY VOLTAGE SELECTIVE lIMPIJIF/[ER Filed Jan. 18, 1949 I 248I0/2/46 5a T f rn..

RESET/PULSE @EC/90E DEC/IDE INVENTOR ATTORNEY Patented June l0, 1.952

VOIVTAGE SELECTIVE AMPLIFIER Olin L. MacSorley, Collingswood, N. J., assignorto -Radio yCorporation of America, a .corporation of Delaware` Applicationilanuary 18,1949, Seriajl'No. '71,1106

1 Claim. 1

This invention relates to amplifiers and .more specifically it relates -to rmeans for selecting'voltages of predetermined-amplitudes.

Many circuits, which are operated by signals derived from amplitude selection of incoming voltages, require pulses of a particular polarity. To accomplish this requirement itis -necessary to provide at times a surplusamplierstage to reverse polarity. Also incircuits of the prior .ar not enough gain can berealized'in operation of a single stage to warrant practicalapplication of a single stage selector ampliiierfcircuit. .It is accordingly the purpose of my inventionto .correct these inadequacies .in a'novelmanner and to provide an economical means forsobtaining. amplificaltion of selected voltages.

An object of my. invention is to .provide an 'amplifier stage which willhave frequency. response great enough to amplify a .square vwave .input voltage without objectionable distortion.

One object of my invention is to provideavoltage selector stage .in .which output and input signals are of the same polarity.

Another object is tosupplya voltage selector stage having a large signal output.

A still further object of -myinvention is to furnish economical and practical `means whereby selection and ampliiication of an input voltage may be attained.

Other objectsandfeatures ofzmy inventions/vill ce set forth in theensuingdiscussion.

Briefly one specicembodiment ofmyiiinvention which I haveusedior .purposes ofiillustration comprisesa resistance coupled ampliercircuit in which aregenerative feed back voltage is provided and in which a biasvoltage is used to reject unwanted signalvoltages. My illustrated embodiment Valso provides-for -inputand output polarities of the samephaserelationship.

rihe features of my invention which I consider are set forth with particularity in the appended claim. The invention itself, however, both as to its organization and its method of operation, will be best understood from the following Adescription of a preferred embodiment, when read in connection with the accompanying drawings wherein like reference characters designate similar parts throughout and in which:

Figure 1 is a schematic representation of an embodiment of my selector stage.

Figure 2 shows the relative amplitudes of typical input and output voltages in a selector stage.

Figure 3 represents a circuit comprising a three decade divider system in which my selector stages are used.

Referring more specically to Figure 1, there yis shown an electron tube .I Ahaving a grounded grid, va cathode impedance consisting of two resistors v3 and-5 connected toground, and an outputfimpedanceconsisting of two resistors? .and il connectedto B+. Input voltage En' is inserted through a capacitor Il directly .to the cathode and output voltage is taken directlyfromltheplate 4through ya capacitor I3. One Vside of both the input and output voltage is grounded, ground herein beingused to-denote the voltagereference level. A capacitor l5 is connected from the junction of theanoderesistorsto the cathode. From vthe junctionv of the cathode resistors a resistor Il is connected to the B+ anode voltage supply, across which resistor two capacitors .I9 .and 2l va'ieconnected'in'.series.L The common connection betweenfcapacitors i9 and 2| .isgrounded AIn FigureZ, a typicalinput voltage Waveform is shown. Ea, andits corresponding outputwaveform, Eb, as taken from a selector stage as shown in Figure l.

.Figure 3 shows .a 4three decadedividersystem similar to `that described .in my. copending .application Ser. rNo. '749,849,..filed'fMay 23, 1947. In

this .figure 4 cascadepdecadesl, 3l .and .'3'3 have connections going .throughchannel resistors 3l, :39 and 4l to .theinputiof corresponding selector stages 423,..215,.and 2l, suchv asshown. in Figure-1, .wh'ichfare connected in cascade. .The .output from the last selectorstage .21 Ais connected to a clipper, inverter, thyratron stage 35 from which -connections are made. to all of .thedecades The .following .description of operation will be .based `on .theabove' .figures AssumeV a Vvarying voltage as shown in Figurez, applied at lthe ter- .This inputvoltaee will enough to;.o.ver.come anygridbias assume that the cathode resistors@ and5 are proportioned so that current flows only during the variation i2 in Figure 2. It is to be understood that the ratios of resistors Il and 5 also will affect the cutoff point by changing the grid bias on the tube.

This current ow will cause a voltage drop across the output impedance resistors 1 and 9 which will cause the signal plate voltage to go negative with respect to ground, due to the coupling capacitor I3. The A. C. voltage change across resistor S Will appear through the regenerative feedback capacitor l 5 across the cathode resistor 3, where it will add in the same phase to Es, thus producing a greater change in plate current providing a large amplication illustrated by the corresponding output variations l2 in Eb. Both the input and output voltages `are of the same phase relationship in this embodiment.

If voltage variation I4 occurs in Ea, the positive change in Ea. produces a decrease in plate current, which produces a decrease in voltage across the resistor 9, which change appears across resistor 3 to add to the change of Ea and hasten the cutting off of plate current. In this manner a square Wave input signal may be amplined with little distortion. It is to be understood, however, that my invention is not to be limited to square wave input voltages.

When the output signal is taken from the anode to ground, the original signal somewhat attenuated appears at the output terminals during the time the tube is cut off. The relative amplitudes of the respective pulses however have lsuch a large ratio that such change may be neglected in all ordinary applications of such a.

circuit.

The voltage amplitude to be selected may readily be predetermined and set by choosing the proper resistors l1 and 5. Obviously, any other type of bias voltage might be used and does not need to be the D. C. voltage drop across the resistor-capacitor combination 5 and I8 as shown in Figure i.

As hereinbefore described, the main advantages of this circuit are that the desired signal is amplified without reversal of phase and that the amplincation is greatly increased by use of the regenerative feedback. Possibility for degeneration is also decreased in this embodiment by grounding the grid.

As an application of my selector stage, Figure 3 shows a three decade divider system which is commonly known in the art. However, it is not to be limited to such a use and has utility whenever signal selection and amplication is needed.

Input voltage of the first cascaded selectoramplifier stage, shown in the block 23, is taken from the rst cascaded decade, or binary group 29, through the resistors 31. Input voltages to the subsequent selector stages and 21 are taken from the corresponding decades 3l and 33 in like manner. At the output of the last selector stage a thyratron circuit 35 or similar clipper-inverter stage is used to provide a reset pulse, which is inserted into each of the cascaded decades.

When the voltage input to any selector stage becomes greater than the predetermined operating voltage for that stage, the resulting operation will produce an output voltage which is mixed at the succeeding stage with the decade voltage. In such manner the input signal may be divided, as desired, by selection of proper decade values. Upon completion of the complete cycle a pulse is derived from the output voltage of the last selector-stage 21 which is used to reset the decade system.

In describing herein an embodiment which 5 is brieiiy a regenerative, grounded grid, selective amplifying circuit, it Will be understood that there may be suggested to those skilled in the art certain modifications which will not constitute a departure from the spirit of my invention.

Having thus fully described the nature, construction and operation of my invention, I wish to secure by Letters Patent and claim:

A regenerative signal amplier for selectively amplifying signal voltages of less than a predetermined amplitude comprising, in combination, an electron tube having an anode, a cathode and a control grid, said control grid being connected to a point of reference potential, a signal input circuit coupled directly between said control grid and said cathode, an output circuit coupled directly between said anode and said point of reference potential, cathode resistor means connected between said cathode and said point of reference potential, a source of directcurrent energizing means having positive and negative terminals, said negative terminal b eing connected to said point of reference potential, bias determining means for eiecting selective famplication of voltages less than said prede- 30 termined amplitude including a fractional part of said cathode resistor means connected between said positive and negative terminals, output resistive means connected between said anode and said positive terminal, capacitive regenera tive feedback means connected between said cathode and an intermediate point on said out put resistive means, a second capacitive means shunting said fractional part of said cathode resistor means, and a third capacitive means connected between said positive and negative terminals.

OLIN L. MACSORLEY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,276,565 Crosby Mar. 17, 1942 2,282,381 Root May l2, 1942 2,289,301 Barber July 7, 1942 2,298,629 Schaper Oct. 13, 1942 2,354,483 Schock July 25, 1944 OTHER REFERENCES Terrnan, Radio Engineering, 2nd edition, 1937, McGraw-Hill Book Company (p. 468, Fig. 259:1). (Copy in Div. 51.) 

